1. V.S. Soldatov, V.A. Bychkova, Ion Exchange Equilibria in Multicomponent Systems, Nauka and Tekhnika, Minsk, 1988 (Russian).
2. K. Dorfner, in: K. Dorfner (Ed.), Ion Exchangers, Walter de Gruyter, Berlin, 1991, p. 7.
3. N.F. Chelischev, Ion Exchange Properties of Minerals, Nauka and Tekhnika, Moscow, 1973 (Russian).
4. J.X. Khim, Analytical Ion Exchange Procedures in Chemistry and Biology, Prentice Hall, Englewood Cliffs, NJ, 1974.
5. The Separation of Rare Earths by Ion Exchange. V. Investigations with One-tenth Per Cent. Citric Acid-Ammonium Citrate Solutions1